If you installed it correctly, you should be able to start the MapReduce perspective and Map/Reduce view. Both are under Window > Open Perspective and Show View respectively.

Click the blue elephant on the upper right corner of the Map/Reduce view. It'll bring up a configuration window.

Type in any name for the the Location Name. I just called it localhost cluster.

Set the port numbers for Map/Reduce Master and DFS Master. Look in your conf/hadoop-site.xml for "mapred.job.tracker" and "dfs.default.name" respectively. If not in that file, then it is probably in hadoop-default.xml or hadoop-env.xml.

Click "Advanced Parameters" tab and set the "mapred.job.tracker" parameter. For some reason it doesn't automatically change when you change it in the "General" tab.

User name should be whoever owns hadoop. For me, it is just my login, others make a separate "hadoop" user for hadoop.

If you have done everything correctly, you should be able to click the triangles on the left to span the hierarchy view.